1. Field of the Invention
This invention relates to a semiconductor light emitting device and its manufacturing method, and more particularly, to a semiconductor device using a fluorescent material and its manufacturing method.
2. Related Background Art
Light emitting devices combining a semiconductor light emitting element like LED (light emitting diode) and a fluorescent material are remarked as inexpensive and long-life light emitting devices, and they are being used widely. Among semiconductor light emitting devices, those for emitting white light are especially regarded hopeful for various ways of use as light emitting devices that can substitute for fluorescent lamps or as light sources of display devices. Semiconductor white light emitting devices use a structure combining a semiconductor light emitting element for emission of blue light or ultraviolet light (UV emission) and a fluorescent material excited by light emitted by the light emitting element. For example, semiconductor white light emitting devices generally used today include those of a structure combining a semiconductor blue light emitting element made of GaN semiconductors and a YAG fluorescent material. Semiconductor white light emitting devices of this type realize white light by color mixture obtained from blue emission spectrums near the center wavelength of 450 [nm] from light emitting elements and broad spectrums having peaks near the wavelength of 560 [nm] which are emitted from YAG fluorescent materials in response to emission of the light emitting elements.
In current semiconductor white light emitting devices, fluorescent materials are usually coated around the semiconductor light emitting element. These devices, however, are subjected to differences in thickness of fluorescent materials through which light from semiconductor light emitting elements pass, and involve the problem of variance in color tone depending on view angles.
Semiconductor light emitting devices are often used in form of an array. In this case, different color tones of light emitting devices, even if small, are easily visible to naked eyes, and it has been desirable that differences in color tone are minimized. Especially with white light emitting devices, variance in color tone is more visible, and it has been inconvenient that color tone changes depending upon view angles.